Disk drive data storage products are becoming more mobile and portable with an increased emphasis on disk storage capacity, data transfer rate, low power consumption and ruggedness. Typical applications include digital cameras, personal digital assistants, personal media players and mobile phones. Most high capacity data storage products are hard disk drives (HDDs).
An HDD utilizes storage platters whose substrates are composed of aluminum or glass and whose thicknesses are more than 0.3 mm. The hard disk platter can be machined to a required flatness and polished to a very smooth surface finish as required for high density recording. The recording head in an HDD is housed in a slider with air-bearing surfaces facing the disk and flies nominally without contact over the disk on a very thin film of air. The combination of a very flat and smooth high-speed disk surface together with a low flying height slider then provides for high storage density and high data transfer rates in the HDD. However, low power consumption and increased slider-disk interface robustness are best provided by a thin flexible recording medium. The most common flexible recording medium is composed of a plastic substrate, such as Mylar, and is referred to as a floppy disk. However, Mylar is a relatively soft material and cannot be polished to the same surface finish as a disk with an aluminum or glass substrate, and thus cannot support the same densities and data rates as a hard disk. In, addition, Mylar is an anisotropic material, and this further limits its possible storage densities.
The metal foil disk described by U.S. Pat. No. 5,968,627 to Nigam et al., the entire disclosure of which is hereby incorporated for all purposes as if fully set forth herein, is a storage medium alternative that combines some of the best properties of both the hard disk and the floppy disk. The metal foil disk makes use of a thin metal substrate with isotropic properties together with recording layers typical of a hard disk. It requires less operational energy than a hard disk due to reduced rotational inertia while providing storage densities and data transfer rates typical of the hard disk. In addition, the metal foil disk, due to its dynamic flexibility, offers increased mechanical shock resistance as compared to a hard disk. And manufacturing cost of the metal foil disk promises to be less than that of the hard disk due to its decreased material cost and process advantages (see U.S. Pat. Nos. 5,968,627 and 6,113,753 to Washburn, the entire disclosure of which is hereby incorporated for all purposes as if fully set forth herein). The design of optimized opposed slider air-bearings for high-speed recording on a metal foil disk was reported recently and show clear advantages of the metal foil disk over the hard disk for two-sided recording (see White, J., 2006, “Design of Optimized Opposed Slider Air Bearings for High-Speed Recording on a Metal Foil Disk,” ASME Journal of Tribology, 128, pp. 327-334; the entire disclosure of which is hereby incorporated for all purposes as if fully set forth herein).
There are, in addition, data storage applications that are best served by single-sided recording. The configuration for single-sided recording consists of a single recording head that exchanges data with one side of a recording disk. Applications include situations where storage requirements 1) can be achieved by data storage on a single side of a disk and 2) involve applications where tight dimensional constraints on the disk drive prohibit the presence of a recording head and its associated mounting device on each side of the disk. Use of a conventional recording head slider assembly for single-sided recording on a high-speed flexible disk presents a fundamental problem, because the air-bearing surface of the slider produces a net transverse (perpendicular to plane of the disk) force to the disk. This causes the disk to deflect and can result in flying height and stability problems at the slider-disk interface. And the migration to higher disk rotational speeds exacerbates this problem. In cases of single-sided recording where disk drive overall dimensional requirements are not a concern, an air-bearing slider or other hydrodynamic pressure pad opposing the data head slider can be used to balance the transverse load acting on the disk due to the data head slider so as to minimize disk deflection and instability. However, significant cost savings can be achieved if all air-bearing requirements can be eliminated from the non-data side of the disk. In addition, a one-sided air bearing provides for decreased operational energy requirements through a decrease in air drag on the rotating disk.